The invention relates to resonant-tunneling electronic transporters using lateral coupling between guided and localized states.
A striking analogy exists between electromagnetic waveguiding in dielectric materials and electronic waveguiding in semiconductor nanostructures. While electromagnetic (EM) waves can travel inside a dielectric waveguide such as an optical fiber, electrons (or electronic wavefunctions) can propagate inside an electronic waveguide such as a quantum wire. For reference, see Eugstar et al., xe2x80x9cTunneling spectroscopy of an electron waveguidexe2x80x9d, Physical Review Letters, vol. 67, pp. 3586-89 (1991). It has been demonstrated recently that EM waves can selectively be transferred from one dielectric waveguide to another by using a resonant coupling element between the two waveguides. Similar effects can be achieved in the electronic device as well.
Progress in nanofabrication technology has allowed electronic devices to be fabricated with a size on the order of 10 nanometers. For reference, see S. Datta, Electronic Transport in Mesoscopic Systems, Cambridge University Press, Cambridge, U.K., 1995). As the size of the device becomes smaller, the quantum mechanical nature of electrons becomes important. In other words, in these devices, electrons behave as a wave, rather than as a classical particle.
Due to the wave nature of the electrons, devices such as electronic waveguides, and electronic resonators, have been constructed and demonstrated. Using these waveguides and resonators, a variety of devices have been fabricated and tested. One example is a waveguide coupler, which directly side-couples two waveguides together to transfer electrons from one waveguide to the other. See, Eugster, et al, xe2x80x9cOne-dimensional to one-dimensional tunneling between electron waveguidesxe2x80x9d, Applied Physics Letters, vol. 64, p. 3157 (1994). Another example is to use the electronic resonator as a narrow-band transmission filter, which selectively transmit electrons through the resonator at the resonant energy, while suppressing the transmission of electrons at other energies. See, Goldhaber-Gordon et al., xe2x80x9cKondo effect in a single-electron transistorxe2x80x9d, Nature, vol. 391, pp. 156-159 (1998).
An object of the present invention is to show that electrons can be transferred between electronic waveguides or between different ports of the same waveguide via a resonant coupling element. The invention provides an electronic device which allows for electrons of different energies to be transported to different ports. The invention relies on the use of a resonant coupling element, such as an arrangement of quantum dots, positioned between two electronic waveguides. Two such types of electronic transport devices (or transporters) are presented. The first type has two ports, while the second type has four ports.
Accordingly, the invention provides an electronic transportor that allows for the resonant tunneling of electrons between guided states, such as those found in a quantum wire or a line defect in a solid, and localized states, such as those found in a quantum dot or a point defect in a solid, using lateral coupling. In some embodiments, the transporter allows electrons of different energies to be transported to different ports of associated waveguides. In other embodiments, the transporter allows electrons of different energies to be transported at different phases.
These and other objects, features and advantages of the present invention will become apparent in light of the following detailed description of preferred embodiments thereof, as illustrated in the accompanying drawings.